JP4045917B2 - Liquid component concentration measuring device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a component concentration measuring apparatus useful for managing the component concentration of a solution such as a chromium plating solution, and more particularly to a component concentration measuring apparatus in a liquid by a simple measuring method using sound speed suitable for in-line measurement.
[0002]
[Prior art]
Chromium plating is widely used as a decorative plating using luster or industrial plating using physical properties such as corrosion resistance and wear resistance. For the management of the plating solution, a method by specific gravity measurement is generally used, and a component determination method by titration is also performed as necessary.
[0003]
Especially in industrial plating, it is indispensable to maintain the plating bath composition within a certain range in order to maintain the quality of the plating film. For this purpose, the concentration of components in the plating bath (plating solution) must be accurately measured. However, all the conventional methods for measuring component concentrations in liquids have some disadvantages industrially.
[0004]
For example, the method for measuring the concentration of components in the liquid by measuring the specific gravity is a method for measuring the specific gravity of the liquid using a float balance called a Baume meter. Basically, the density of the plating solution such as chromic anhydride solution (specific gravity) ) Is changed by the component concentration. This method is a simple measurement method in which a scale is floated in the liquid and is widely used. However, from the viewpoint of accuracy, it is difficult to evaluate the influence of components other than chromic anhydride, and the measurement It was also difficult to control the result by electrically feeding back the result.
[0005]
Moreover, the measuring method of the component concentration in the liquid by titration is a method of measuring each component of chromic anhydride concentration, trivalent chromium concentration and sulfuric acid concentration in chromic anhydride solution by titration, and quantitative evaluation of each component. Although there is an advantage that it can be performed, it was difficult to measure constantly because it took a sample from the plating solution (sampling) and performed measurement offline, and because it required humans and time for the titration work .
[0006]
Therefore, as a method that can solve these problems and can be used for in-line measurement control, there are several methods for obtaining the concentration by measuring the speed of sound using the relationship between the speed of sound in the liquid and the density of the liquid. It has been put to practical use in the field.
[0007]
However, when applied to a chrome plating solution, it is expected that a very complicated algorithm and a lot of correlation data will be required due to the temperature dependence of the sound velocity in the solution, and evaluation of the influence of subcomponents. For this reason, it was difficult to put it to practical use because it was necessary to use it together with other analytical methods.
[0008]
Here, as a composition of the chromium plating solution, a plating solution generally used for hard chromium plating will be described as an example. Specifically, the composition of the plating solution is, specifically, chromic anhydride of 250 ± 100 g / Liters and sulfuric acid in the range of 2 to 10 milliliters / liter.
[0009]
As a result of detailed investigations on the correlation between the concentration of the aqueous solution and the speed of sound in the liquid of the main component chromic anhydride among the components in the liquid used for chromium plating, the present inventors have determined the chromic anhydride concentration as the speed of sound. It has been found that it is possible to measure by.
[0010]
However, it has been found that when this is applied to in-line measurement, noise is superimposed on the measurement value due to the influence of bubbles generated in the process, and accurate sound speed measurement is difficult.
[0011]
In order to solve this problem, several countermeasures have been proposed. Broadly speaking, there are removal of the influence of bubbles by improving the algorithm for measuring the speed of sound and removal of the bubble main body generated in the solution to be measured. .
[0012]
The removal of the influence of bubbles by improving the sound velocity measurement algorithm is basically to perform data processing so that the reflected wave signal that is attenuated by bubbles in the ultrasonic signal can be ignored. It is divided into several categories according to the logic of discrimination between normal signals that are not received and abnormal signals that are attenuated.
[0013]
In general, normal signals are considered to have little repeated change in a short time and abnormal signals are considered to have large changes, so that they can be identified by the dispersion of sound velocity values within a certain time. This is applicable only when an appropriate number exists in a certain time. It is also possible to distinguish normal signals and abnormal signals based on the intensity ratio due to attenuation, but this method has a problem that it is difficult to distinguish it from several-order reflected waves. However, at present, it has not reached a level where stable measurement is possible for a system in which many microbubbles exist.
[0014]
As a method for removing bubbles in the solution to be measured, a method by pressurization has been conventionally proposed, and means for assisting this may be used in combination. This method is structurally complicated because the pressure is applied with the flow path closed, and it is easy to use, including safety measures, in the process of handling highly oxidative dangerous liquids such as chromic acid. Have difficulty.
[0015]
Bubbles can be removed by standing in the atmosphere, but this takes time to defoam, so continuous in-line measurement is not possible, and intermittent measurement is required. In many cases, the temperature of the liquid greatly decreases and exceeds the temperature-dependent linear range of the sound velocity, and accurate measurement is difficult.
[0016]
[Problems to be solved by the invention]
In order to solve this problem, the present inventors have experimentally evaluated the degree of defoaming in the open continuous flow path. As a result, the combination of the low flow pump and the long flow path has an effect on the sound velocity measurement. It was found that there was no air bubble removal. That is, as a mechanism for removing bubbles in the liquid, it is a liquid component concentration measuring device for a chromium plating solution having a removal tank provided with a return channel at normal pressure.
[0017]
This method is a maintenance-free method of measuring the speed of sound in-line, and is a method of measuring the concentration of a component from a single physical quantity of only the speed of sound, allowing continuous measurement and monitoring without the need for a complex pressurization mechanism. It is excellent in that it is.
[0018]
However, it requires a bypass mechanism and the complexity of the measurement device using a liquid feed pump, the delay of measurement timing due to the defoaming time, and an expensive sensor is required for each of the three tanks. There were two problems.
[0019]
An object of the present invention is a device for measuring the concentration of components in a liquid, which simplifies the measurement device, eliminates the delay in measurement timing due to the defoaming time, and eliminates the need for separate expensive sensors in the case of measuring multiple tanks. There is to do.
[0020]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention is a liquid having a method of obtaining the component concentration in the solution 2 from the sound velocity in the solution 2 measured by the sound velocity measuring means 4 disposed in the solution 2 in the measuring tank 1. In the medium component concentration measuring apparatus, the sound velocity sensor unit 5 of the sound velocity measuring means 4 (the ultrasonic oscillation unit 5a and the ultrasonic wave receiving unit 5b arranged to face each other in the vertical or horizontal direction) is used as the liquid level L of the solution 2 in the measurement tank 1. And a depth control means 3 for controlling the arrangement to a certain depth D , and the sound velocity sensor portion is fixedly arranged at a position at a certain depth below the depth control means. It is a measuring device.
[0021]
The invention according to claim 2 of the present invention is the float 6 (floating body) in which the depth control means 3 floats on the liquid surface L of the solution 2 in the measuring tank 1 in the liquid component concentration measuring device according to claim 1. In the liquid component concentration measuring apparatus, the sound speed measuring means 4 is fixed to a float 6.
[0022]
The invention according to claim 3 of the present invention is the liquid component concentration measuring apparatus according to claim 1 or 2, wherein the solution 2 is a chromic anhydride solution, and the component concentration is measured in the liquid. Is a chromic acid concentration measuring device.
[0023]
[Action]
In order to solve the above problems, the present inventors have developed a solution 2 in which the liquid level of the liquid level L varies in a measurement tank 1 (solution storage tank, treatment tank) that stores the solution 2 to be measured. As a result of experimental evaluation of the distribution of the bubbles 2a in the inside and the influence of the solution 2 on the sound speed measurement, the sound speed sensor unit 5 of the sound speed measuring means 4 (the ultrasonic oscillator 5a and the ultrasonic receiver 5b disposed opposite to each other). ) At a certain depth D from the liquid level L of the solution 2, it is necessary to influence the sound velocity measurement due to the presence of many bubbles 2 a generated in the liquid below the certain depth D from the liquid level L. Can be reduced to a certain extent.
[0024]
The liquid component concentration measuring apparatus of the present invention corresponds to the sound velocity measuring means 4 (the sound velocity sensor unit 5 and the ultrasonic waves disposed opposite to each other) corresponding to the fluctuation of the liquid surface level of the liquid surface L of the solution 2 stored in the measuring tank 1. Since the oscillating unit 5a and the ultrasonic vibration receiving unit 5b) are provided with the depth control means 3 such as a float for controlling the arrangement of the oscillating unit 5a and the ultrasonic vibration receiving unit 5b from the liquid level L of the solution 2 at a constant depth D, the sonic velocity sensor unit 5 of the sonic velocity measuring unit 4 is provided. Can always be maintained at a certain depth D from the liquid level L, and the influence on the sound velocity measurement due to the presence of a large number of bubbles 2a generated in the solution 2 below the certain depth D from the liquid level L can be reduced to a necessary level. it can.
[0025]
The device of the present invention can be used for the component concentration measurement of all solutions in which the component concentration can be measured by the speed of sound among the open system solutions 2 containing the bubbles 2a. In a measurement tank 1 such as a storage tank for storing a plating solution (plating bath), when the concentration of chromic acid in the chromic anhydride solution as the plating solution is a measurement target, the liquid level L is constant. The influence on the sound speed measurement due to the presence of a large number of bubbles 2a generated in the plating solution 2 having a depth of less than D can be reduced to a necessary level.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the liquid component concentration measuring apparatus of the present invention will be described in detail below with reference to FIG. 1. The apparatus of the present invention is used as a measuring tank (treatment tank) such as a plating solution (plating) such as a chromic anhydride solution. A float 6 (floating body) is provided as a depth control means 3 on the liquid level L of a predetermined solution 2 such as a plating solution (plating bath) stored in the storage tank 1. It ’s floating.
[0027]
As shown in FIG. 1, the sound speed measuring means 4 is fixedly attached to the float 6 which is the depth control means 3, and the sound speed sensor unit 5 of the sound speed measuring means 4 is attached to the lower part outside the float 6. 2 is fixedly arranged at a position of a certain depth D (depth) from the liquid level L, and the sonic sensor unit 5 is in the liquid at a constant depth D from the liquid level L regardless of the displacement of the liquid level L. The speed of sound can be measured.
[0028]
The sound speed data signal measured by the sound speed sensor unit 5 of the sound speed measuring unit 4 is output from the sound speed measuring unit 4 and connected to the sound speed measuring unit 4 for transmitting the measurement signal transmission W (signal cable, necessary). Accordingly, the measurement reference voltage to the sound velocity sensor unit 5 is also provided to the concentration measurement operation control means 7 through a wiring system that can supply the measurement reference voltage.
[0029]
The concentration measurement operation control means 7 includes a central control processing unit 8 (CPU), a sound speed data signal processing unit 9, a memory unit 10, and a measured concentration display unit 11 (a CRT display monitor for outputting measurement data and a liquid crystal display). Monitor, printer, etc.).
[0030]
The sound speed data signal in the liquid at a certain depth D from the measured liquid level L of the solution 2 from the sound speed measuring means 4 is input to the sound speed data signal processing unit 9 and is controlled by arithmetic processing control by the central control processing unit 8. The sound speed data signal processing unit 9 reads out the sound speed-concentration conversion table stored in the memory unit 10 in advance, and the sound speed data measured by the sound speed measuring means 4 is used as the solution at the depth D of the liquid 2. The solute component concentration in the solution is calculated by conversion into density data [solute mass (solute mass of one kind of solute component) / solvent amount] (solution concentration data).
[0031]
【Example】
Specific examples of the liquid component concentration measuring apparatus of the present invention will be described below.
[0032]
<Example 1>
As shown in FIG. 1, a chromium plating solution 2 having a temperature of 60 ° C. containing chromic anhydride as a main component was stored as a solution in a plating bath 1 having a depth of 50 cm.
[0033]
Moreover, the plating solution 2 in the plating bath 1 was circulated and sent by a plating solution circulation / feeding means (not shown) equipped in the plating bath 1. In the plating solution 2 having a depth of less than 10 cm from the liquid level L of the plating solution 2, a large number of bubbles 2a were observed.
[0034]
On the liquid surface L of the plating solution 2, a 2 MHz ultrasonic wave oscillating unit 5 a (oscillator) and an ultrasonic vibration receiving unit 5 b are arranged as the sound velocity measuring means 4 so as to face each other with the plating solution 2 interposed therebetween. A float 6 (depth control means 3) is attached to the sonic sensor unit 5 (sound speed meter) configured so that the depth D is 20 cm from the liquid level L of the solution 2 and floats. The speed of sound in the plating solution 2 at a depth of 20 cm was measured in a state where the liquid level was changed up and down.
[0035]
The measured sound speed data signal passes from the sound speed measuring means 4 through the connection cable W, the central control processing section 8 (CPU), the sound speed data signal processing section 9, the memory section 10, and the measured concentration display in the apparatus of the present invention. This is input to the sound velocity data signal processing unit 9 of the concentration measurement operation control means 7 having the unit 11 (CRT display monitor for measurement data output, liquid crystal display monitor, printer, etc.).
[0036]
Subsequently, the sound speed data signal processing unit 9 inputs the actually measured sound speed data in the plating solution 2 and a temperature-corrected sound speed-concentration conversion table (the memory unit 10) that represents the relationship between the sound speed and the concentration created in advance. The chromic anhydride concentration was calculated based on a sonic-concentration conversion table for a chromium plating solution having a temperature of 60 ° C. containing chromic anhydride as a main component. The sound speed data over time at this time is shown in FIG.
[0037]
<Comparative Example 1>
As Comparative Example 1, measurement was performed by fixing the sonic sensor 5 similar to that of Example 1 at a fixed position regardless of the fluctuation of the liquid level of the plating bath having the same depth as that of Example 1. Except for the above, the speed of sound in the chromium plating solution 2 having a temperature of 60 ° C. containing chromic anhydride as a main component was measured in the same manner as in Example 1 above, and the concentration of chromic anhydride was calculated based on the conversion table. The temporal sound velocity data at this time is shown in FIG.
[0038]
<Measurement results>
When the liquid level L is high (that is, the position of the sound speed sensor 5 from the liquid level L is deep), the sound speed data of Comparative Example 1 is stable, but the liquid level L is low (that is, the sound speed sensor 5 is a bubble 2a). Stable measurement data could not be obtained due to the influence of the bubbles 2a.
[0039]
In Example 1, there was almost no data fluctuation, and stable measurement data was obtained. The chromic anhydride concentration measured in Example 1 was ± 0.3% as a result of testing with a solution having a known concentration, and had accuracy and reproducibility necessary for management.
[0040]
【The invention's effect】
The apparatus for measuring the concentration of components in the liquid of the present invention does not require a complicated solution bypass mechanism particularly in the measurement of a corrosive solution, and can simplify the apparatus as compared with a conventional measurement method with a bypass mechanism, and a corrosive solution. In this measurement, the device structure is simplified.
[0041]
In addition, the liquid component concentration measuring device of the present invention can easily move one sonic velocity measuring means (sonic velocity sensor unit) even in measurement in a plurality of basins with different types of measurement tubs (solution storage tanks, plating baths, etc.). Since measurement is possible, it becomes unnecessary to prepare a plurality of expensive sensors, and the measurement cost can be reduced.
[0042]
In addition, the measurement time required to pass through the bypass channel can be omitted and the state of the measurement tank can be grasped in real time, as in the measurement method with a bypass mechanism, so that the solution change in the tank during the solution handling process such as plating bath treatment Appropriate response to (solution concentration, change in component concentration in liquid, change in liquid level, etc.) can be quickly made.
[0043]
Compared to the off-line measurement method used in conventional liquid component concentration measurement devices, the time required for sampling operations for solution and measurement operations by humans can be omitted, and physical quantities can be automatically collected at the same time. Since the data signal is electrically transmitted directly from the sound speed measurement means (sound speed sensor unit) to the concentration measurement operation control means, it can also be used for feedback control such as solution concentration adjustment and component concentration adjustment based on the measured physical quantity. become.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a liquid component concentration measuring apparatus according to the present invention.
FIG. 2 is a graph showing the relationship between the sound speed measured by the liquid component concentration measuring apparatus of the present invention and the measurement elapsed time.
FIG. 3 is a graph showing the relationship between the sound speed measured by a conventional liquid component concentration measuring device and the measurement elapsed time.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Measurement tank (solution tank) 2 ... Solution 2a ... Bubble 3 ... Depth control means 4 ... Sound speed measurement means 5 ... Sound speed sensor 5a ... Ultrasonic oscillation part 5b ... Ultrasonic wave receiving part 6 ... Float 7 ... Concentration measurement operation control means 8 ... Central control processing unit (CPU) 9 ... Sound speed data signal processing unit 10 ... Memory unit 11 ... Measurement concentration display unit (display)
L ... Liquid level D ... Depth W ... Signal cable

Claims (3)

In the in-liquid component concentration measuring device that calculates the component concentration in the solution from the sound speed in the solution measured by the sound speed measuring means arranged in the solution in the measurement tank, the sound speed sensor unit of the sound speed measuring means is It is provided with a depth control means for controlling the placement at a constant depth from the liquid level of the solution in the measurement tank , and the sound velocity sensor unit is fixedly arranged at a position at a constant depth below the depth control means. In-liquid component concentration measuring device. 2. The liquid component concentration measuring apparatus according to claim 1, wherein the depth control means is a float floating on the liquid surface of the solution in the measurement tank, and the sound speed measuring means is fixed to the float. An apparatus for measuring the concentration of a component in liquid. The liquid component concentration measuring apparatus according to claim 1 or 2, wherein the solution is a chromic anhydride solution, and the measurement target of the component concentration in the liquid is chromic acid. Concentration measuring device.

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